Conventionally, optical networks rely on in-band communication channels for a variety of Operations, Administration, Maintenance, and Provisioning (OAM & P) functions as well as for control plane signaling and the like. Exemplary in-band communication channels include the Data Communication Channel (DCC) in Synchronous Optical Network (SONET) and Synchronous Digital Hierarchy (SDH) and the General Communication Channel (GCC) in Optical Transport Network (OTN). In contrast to SONET/SDH where the DCC has a constant data rate on the order of 1 Mb/s, the GCC data rate depends on the OTN line rate, i.e., Optical channel Data Unit (ODU) data rate. For example, GCC data rate in the case of an Optical channel Data Unit-1 (ODU1) is ˜333 kb/s, for Optical channel Data Unit-2 (ODU2), its data rate is ˜1.3 Mb/s, for Optical channel Data Unit-4 (ODU4), its data rate is ˜13 Mb/s, and the like. In the past with SONET/SDH, the in-band communication channels were first used solely for OAM & P data between nodes and network management. Here, the low data rate of SONET/SDH DCC sufficed. With OTN, the in-band communication channels evolved to also carry control plane signaling in addition to OAM & P data. Here, the higher GCC data rate in OTN allowed the addition of control plane signaling with the OAM & P data.
Additional applications are evolving, such as SDN, which will require additional bandwidth on the in-band communication channels. Specifically, SDN is a centralized control architecture which requires the gathering and backhaul of data from the nodes to a centralized location/server, i.e., “hubbed” traffic flow patterns. It is also expected that SDN will provide a rich suite of flexible applications, such as in combination with Network Functions Virtualization (NFV). The conventional GCC data rate in OTN will have difficulty in handling the hubbed nature of SDN and the evolving bandwidth requirements, in addition to control plane signaling, OAM & P data communication, etc.
Thus, there is a need for a higher rate in-band communication channel. Unattractive options include: 1) the OTN frame could be modified to allow for a higher rate OTN/GCC communication channel, but this is difficult due to standardization; 2) the line frame format (proprietary to each system vendor) could be designed to include a communications channel time slot meaning a higher required line rate, with the requisite required extra link margin; or 3) a dedicated SDN communication channel could be allocated in the client payload, but would consume valuable client/customer transport bandwidth, and such an approach has generally been commercially unacceptable at the transport layer.
Thus, there is a need for a high-capacity in-band communication channel in optical networks.